low pass filter is term which Big Guys would use, but we Peasants ...... we must beat slightly around the bush 
Hi - sorry folks but just trying to confirm things. I was told by the shop i bought the chassis from that all i need is just connect the 240v (UK) to the two terminals and the needle will be in the middle. Are you trying to do something different? or are they suggesting incorrectly?
to philiphifi #42
If you want to measure your mains AC voltage getting into your amp? - then it is the right way.
But most of us classA-amp- freaks want to know, if our amp has reached the correct amount of bias (in Amperes). This is measured over the bias resistor.
You measure the voltage over your bias resistor and then use Ohm's law: I = U/R or Amperes = Voltage (over resistor) divided by R (resistance of resistor you are measuring over). Then you know how this single MosFet is biased.
Now you can connect your meter to the bias resistor and adjust it, that it shows
mid value if voltage over bias resistor is 'correct' (depending on your necessary
amount of bias for 'true' classA - operation).
I hope I described it correct and understandable? 🙄
Greets
Dirk
If you want to measure your mains AC voltage getting into your amp? - then it is the right way.
But most of us classA-amp- freaks want to know, if our amp has reached the correct amount of bias (in Amperes). This is measured over the bias resistor.
You measure the voltage over your bias resistor and then use Ohm's law: I = U/R or Amperes = Voltage (over resistor) divided by R (resistance of resistor you are measuring over). Then you know how this single MosFet is biased.
Now you can connect your meter to the bias resistor and adjust it, that it shows
mid value if voltage over bias resistor is 'correct' (depending on your necessary
amount of bias for 'true' classA - operation).
I hope I described it correct and understandable? 🙄
Greets
Dirk
hi Dirk
Ah - got it. thanks very much. i don't know if the class A bias drifts over time like some of the valve amps. I thought for solid state it is stable so just set and leave.
Ah - got it. thanks very much. i don't know if the class A bias drifts over time like some of the valve amps. I thought for solid state it is stable so just set and leave.
This is what I've been looking for
! Last year I got support in thread Krell KS-50 to build my amp, see pictures post #9134.Having the Pass Labs look enclosure I also wanted the "class-A metering" but could'nt figure out how to realize it. Now I have some questions before implement what you describe.
I take the signal from one of four bias in 2ch amp. Is this a good enough representation of the total current status? Will the meter nervously jump or be reasonable stable? Is there a risk of introducing any noise or emc at this point that could affect the output quality😕
make it as I described ( series resistor and electolyt cap in parallel), then you'll have answer to all your questions
🙂
if you want periodic check of Iq of both channels , just introduce 2 position switch, maybe on back of an amp
🙂
if you want periodic check of Iq of both channels , just introduce 2 position switch, maybe on back of an amp
Thanks Zen, I didn't see the previous posts. A while ago I saw UGS design of the same feature that looked very advanced to me. I decided to let it rest until now.🙄